THE ANTERIOR VENA CAVA. 701 



— The cartilaijinous plates serve to support, by their two faces and the eanali- 

 culi by which they are traversed, a mass of very close, anastoinosinii^, and con- 

 verging veins, which, from its situation, may he designated the cartilagitioics 

 plt'xus. 



" This cartilaginous plexus is formed by two layers of vessels — a supfrfirial 

 and deep. 



" Superficial cartilaginous layer or plexi/a. — The superficial layer (Fig. 388, 

 3, 4), extended over the external surface of the cartilaginous plates and bulbs, 

 has its origin by innumerable radicles from the veins of that part of the podo- 

 phyllous plexus corresponding to the superficies it occupies. These roots, massed 

 in a very dense network, converge towards the superior portions by diminishing 

 in number and augmenting in volume, and terminate in forming themselves, by 

 the aid of successive anastomoses, into ten or twelve principal branches which 

 again unite into two considerable vessels (Fig. 388, 6), situated at the superior 

 limit of the plexus. These vessels, finally, by their last fusion at the inferior 

 extremity of the first phalanx, constitute the digital vein, the satellite of the 

 artery of the same name (Fig. 388, 5). 



" Considered from below upwards, in a foot previously prepared by injection, 

 the digital vein, divided into two branches, subdivides itself into secondary 

 branches and ramuscules which diverge and spread over the convex surface of 

 the cartilage and coronary cushion, resembling somewhat the disposition of trees 

 trained as espaliers, whose spreading branches are fixed to the walls on which 

 they ramify. 



" The two peripheral branches of the superficial cartilaginous plexus establish 

 communications with the opposite cartilaginous plexus, in contracting direct 

 anastomoses with the branches of the plexus which are symmetrical to them. 



" The anterior anastomosing canals are double and superposed. 



" The most inferior and superficial is constituted by the large vein (Fig 388, 

 3') thrown slantingly across from one plexus to the other in the median plane, 

 and on the external surface of the extensor tendon ; this receives a considerable 

 multitude of venous ramuscles, which emerge from the anterior part of the podo- 

 phyllous plexus. 



" This first communicating vein joins the anterior branches of the carti- 

 laginous plexus. 



" The second communicating vein, situated three-quarters of an inch above 

 the first, and beneath the tendon, is thrown transversely from one anterior 

 branch of the plexus to the other. They open into each other on each side, at 

 the same point where the first communicating vein enters. 



" Sinuous in the whole of its track, sometimes double, and sometimes formed 

 of several confluent veins — as in Fig. 388 — this anastomosing canal serves as an 

 outlet for several deep veins. 



" The anastomosis between the posterior peripheral branches of the cartila- 

 ginous plexus is formed by an irregularly curved and long vein of large calibre, 

 sinuous or broken in its course, but always considerably longer than the distance 

 from the two cartilaginous plates between which it is extended. 



" This posterior communicating vein acts as a confluent to the canals emerging 

 from the cartilaginous bulbs, and to the posterior part of the solar plexus, which 

 throws into it five or six well-developed afferent veins. 



" Deep cartilaginous layer or plexus. — The deep layer of the cartilaginous 

 plexus is formed : 

 47 



